title: Handling the 3-methylcytosine lesion by six human DNA polymerases members of the B-, X- and Y-families.
abstract: Alkylating agents often generate 3-methylcytosine (3meC) lesions that are efficiently repaired by AlkB homologues. If AlkB homologue proteins are not functional, or the number of 3meC lesions exceeds the cellular repair capacity, the damage will persist in the genome and become substrate of DNA polymerases (Pols). Though alkylating agents are present in our environment and used in the clinics, currently nothing is known about the impact of 3meC on the accuracy and efficiency of human Pols. Here we compared the 3meC bypass properties of six human Pols belonging to the three families: B (Pol δ), X (Pols β and λ) and Y (Pols κ, ι and η). We show that under replicative conditions 3meC impairs B-family, blocks X-family, but not Y-family Pols, in particular Pols η and ι. These Pols successfully synthesize opposite 3meC; Pol ι preferentially misincorporates dTTP and Pol η dATP. The most efficient extenders from 3meC base-paired primers are Pols κ and η. Finally, using xeroderma pigmentosum variant patient cell extracts, we provide evidence that the presence of functional Pol η is mandatory to efficiently overcome 3meC by mediating complete bypass or extension. Our data suggest that Pol η is crucial for efficient 3meC bypass.
authors.affiliation: Institute of Veterinary Biochemistry and Molecular Biology, University of Zürich, Winterthurerstrasse 190, 8057 Zürich, Switzerland.
authors.forename: Antonia
authors.initials: A
authors.lastname: Furrer
authors.forename: Barbara
authors.initials: B
authors.lastname: van Loon
mesh_terms: D002460:Cell Line; D003596:Cytosine / Q000031:analogs & derivatives* / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D004249:DNA Damage; D004260:DNA Repair; D004259:DNA-Directed DNA Polymerase / Q000145:classification / Q000378:metabolism*; D006801:Humans; D000094769:DNA Polymerase iota; D000099270:Y-Family DNA Polymerases
chemical_list: D003596:Cytosine; D004247:DNA; D004259:DNA-Directed DNA Polymerase; D000094769:DNA Polymerase iota; C036386:3-methylcytosine; C404302:POLK protein, human; D000099270:Y-Family DNA Polymerases; C112338:Rad30 protein; C000722070:POLI protein, human